Seattle-based Alaska Airlines actually has some of its aircraft with a 13th row and others without. Alaska decided to order Boeing 737-800s and, "due to cancellations by other airlines, Alaska was able to practically buy the first couple right off the assembly line," said Geoff Pettis, Manager of Interior Engineering with Alaska Airlines. "However, this compressed time frame meant Alaska was not able to spec out [design] the cabin as would have normally happened."

To keep the layout consistent, Alaska continued to order new 800's without a 13th row, "but not because of any superstition," Pettis said.

AirTran does not offer a 13th row because passengers had expressed a desire not to sit there. That will be changing when the carrier is acquired by Southwest Airlines later this year. Southwest has stated the seating configuration will be reconfigured on AirTran's aircraft, including the addition of a 13th row.

The number 13 is not the only unlucky number for some cultures, and airlines have responded to that too. Lufthansa, which is based in Germany, does not have a 13th or 17th row. "The reason is that in Italy and Brazil, 17 is regarded as unlucky," Lufthansa spokeswoman Jennifer Janzen explained.

Currently Continental Airlines does not have a 13th row. "Many years ago, apparently, someone decided we wouldn't have a row 13 in our fleet," spokesman Andrew Ferraro told AOL Travel News. "We maintained the row numbering system for consistency as we brought new airplane types into the fleet."

But with the merger of United Airlines and Continental, row 13 might start disappearing on United Airlines's fleet as the two airlines align their seat row numbers to ensure consistency with their new brand.

"I believe the goal of airlines omitting it is to help reduce anxiety that fliers may have," said Matt Daimler, Founder of Seatguru.com. He also pointed out that rarely does the row number actually match the number of rows in an aircraft anyway, given factors such as the extra space taken up by first class.